PROJECT SUMMARY Hearing loss has a profound impact on individuals, causing communication problems, social isolation, and cognitive decline. Microvascular pathology is a significant factor seen in many types of hearing loss, including sound-induced hearing loss, age-related hearing loss, genetic hearing loss, and autoimmune inner ear disease. Normal capillary blood flow is highly controlled by pericytes. The pericytes, specialized mural cells surrounding small blood vessels adjacent to endothelial cells, are vital for normal vascular function. Pericyte pathology, such as pericyte loss or degeneration, is a significant factor in degenerative neural diseases, including Alzheimer's disease and brain dementia. The cochlear microvasculature contains an abundant population of pericytes. However, the role of pericytes in the cochlea, in general, is understudied. In particular, their roles in vascular and hearing function is largely unknown. Using a combination of well-established and cutting-edge techniques, and building on preliminary data produced under R21 support, the proposed five-year research program continues the investigation of mechanisms outlined in our current R21 grant to further explore the role of PCs, PC-related vascular pathology, and angiogenesis in cochlear health. Success in this project will open new clinical options for treatment of aging-, noise exposure-, and genetic vascular deficiency-related deafness in which PCs are compromised.